Copper base alloys

ABSTRACT

The disclosure teaches novel copper base alloys having improved toughness and stress corrosion resistance. The copper alloys contain from 12.5 to 30 percent nickel, from 12.5 to 30 percent manganese, a material selected from the group consisting of aluminum from 0.01 to 5 percent, boron from 0.001 to 0.1 percent, magnesium from 0.01 to 5 percent and mixtures thereof and zinc from 0.1 to 3.5 percent.

United States Patent [191 Shapiro et a1.

[ COPPER BASE ALLOYS [75] Inventors: Stanley Shapiro, New Haven, Conn;

Alan J. Goldman, Silver Springs, Md.; Derek E. Tyler, Cheshire; RichardD. Lanam, Hamden, both of Conn.

[73] Assignee: Olin Corporation, New Haven,

Conn.

[22] Filed: Nov. 5, 1971 21 Appl. No.: 196,002

[52] U.S. Cl 148/325, 75/153, 75/157.5, 75/159, 75/161,75/162,148/l2.7,148/32,148/l60 [51] Int. Cl C22c 9/04, C22f 1/08 [58]Field of Search 75/153, 157, 157.5, 75/15 9,l61,162,164;148/12.7,32.5,160

[56] References Cited UNITED STATES PATENTS 2,234,552 3/1941 Dean et a1.75/159 X FOREIGN PATENTS OR APPLICATIONS 1,092,218 11/1960 Germany75/159 Nov. 13, 1973 578,223 6/1906 Great Britain 75/159 24,220 10/1964Japan 75/159 577,170 5/1946 Great Britain.. 75/159 577,597 5/1946 GreatBritain 75/159 719,979 4/1942 Germany 75/159 OTHER PUBLICATIONSElectrolytic Manganese and Its Alloys, Dean The Ronald Press Co. 1952NY. pgs 146,147, 188-191 Primary Examiner-Char1es N. LovellAttorney-Robert H. Bachman et a1.

[57] ABSTRACT 8 Claims, 2 Drawing Figures PATENTEURM 1 3 I973 UPE. m./b,//I7.

SHEET F 2 I I I I I u m ALLOY A o ALLOY a ALLOY c aooq- A ALLOY 0 ALLOYE cw) O O I I T --4- 150 I I I 200 2/0 0.2% OFFSET V/ELO STRENGTH (KSOLONG/TUD/NAL PROPERTIES INVENTORS STANLEY SHAP/RO ALAN J. GOLDMAN DEREKE. TYLER RICHARD D. LANAM ATTORNEY UPE m. lb. 1/1

PAIENIEBIUV 13' ms 3. 7 72.092 SHEET 2 BF 2 [1 ALLOY A ALL 300-- 0 0yALLOY c A ALLOY 0 Q ALLOY E cw) o A 0 l I O INVENTORS.

STANLEY SHAP/RO ALAN J GOLDMAN DEREK E. TYLER RICHARD D. LANAM I BYWMATTORNEY 1 COPPER BASE ALLOYS BACKGROUND OF THE INVENTION Copper basealloys are known which contain relatively large amounts of nickel andmanganese. Alloys of this type are highly desirable since they arecapable of obtaining yield strengths in excess of 200 ksi upon aging. Inaddition, these alloys appear to have reasonable processing and inparticular are not quench sensitive.

The presence of a marked aging response to obtain high strengths ineopper-nickel-manganese alloys is known. It has been found thatdifferent types of precipitation reactions may occur in this alloysystem, depending on the aging temperature. For example, aging at a lowtemperature, such as 350C, yields a cellular precipitate which nucleatesat the grain boundaries and with time grows throughout the entire grain.The cellular precipitate consists of adjacent lamellae of amanganese-nickel rich phase and the copper-rich solid solution. Aging athigher temperatures, such as 450C., yields mainly finely dispersed,spherical precipitates of the manganese-nickel rich phase within thegrains and only a small amount of the cellular precipitate at the grainboundaries.

However, in any event, the presence of a cellular precipitate at grainboundaries is generally found to have deleterious effects on alloyproperties, such as fracture toughness and stress corrosion resistance.This is indeed found to bethe case in these alloys and is a significantfactor in the limited commercial success which these alloys haveenjoyed. I

It would be highly desirable to develop an alloy within thecopper-manganese-nickel alloy system which has increased fracturetoughness. It would also be highly desirable to improve the stresscorrosion resistance of such alloys.

Accordingly, it is a principal object of the present invention todevelop a copper base alloy containing relatively large amounts ofnickel and manganese.

It is an additional object of the present invention to develop an alloyas aforesaid which is capable of obtaining yield strengths in excess of200 ksi upon aging.

It is a still further object of the present invention to develop analloy as aforesaid which is readily processed commercially and which ischaracterized by improved fracture toughness.

It is a still further object of the present invention to provide acopper base alloy with good stress corrosion resistance, good ductility,toughness and excellent yield strength characteristics.

Further objects and advantages of the present invention will appear fromthe ensuing discussion.

SUMMARY OF THE INVENTION In accordance with the present invention, ithas now been found that the foregoing objects and advantages may bereadily obtained.

The alloy of the present invention consists essentially of from 12.5 to30 percent nickel, from 12.5 to 30 percent manganese, from 0.1 to 3.5percent zinc and a material selected from the group consisting ofaluminum from 0.01 to 5 percent, magnesium from 0.01 to 5 percent, boronfrom 0.001 to 0.1 percent mixtures thereof, balance essentially copper,wherein the nickel to manganese ratio is at least 0.75 and preferably1.0 or higher.

BRIEF DESCRIPTION OF DRAWINGS In the drawings which form a part of thepresent specification:

FIG. 1 is a graph plotting the fracture toughness as a function of yieldstrength for various alloys, representing the properties longitudinal tothe rolling direction; and

FIG. 2 is a similar graph plotting the fracture toughness as a functionof yield strength for various alloys, representing the propertiestransverse to the rolling direction.

DETAILED DESCRIPTION In accordance with the present invention, theforegoing alloy has been found to obtain surprisingly improved fracturetoughness while retaining the excellent strength characteristics of thisalloy system.

This enables the attainment of several significant advantages. The alloyof the present invention is an excellent lower priced replacement forberyllium-copper, with increased fracture toughness. The alloy of thepresent invention achieves levels of fracture toughness approaching highalloy steels which are limited in applicability by poor corrosionresistance. The alloys of the present invention are superior to maragingsteels in marine environments since the alloys of the present inventionare not susceptible to hydrogen embrittlement. In addition, the alloysof the present invention are characterized by excellent stress corrosionresistance.

In accordance with the present invention, the instant alloys containfrom 12.5 to 30 percent nickel, and from 12.5 to 30 percent manganese.Preferably, both the nickel and manganese contents should range from 15to 25 percent. The nickel to manganese ratio must be at least 0.75 andpreferably 1.0 or higher.

The nickel and manganese contents have an affect on aging response,yield strength and workability of the alloys. The lower the manganeseand nickel content, the slower the aging response and lower the maximumyield strength obtainable upon aging, especially below 12.5 percentnickel and manganese. On the other hand, increasing the amount of nickeland manganese has deleterious effects on the workability of the alloysduring processing, especially over 30 percent each of nickel andmanganese.

As indicated hereinabove, the preferred nickel to manganese ratio is 1.0or higher. The maximum aging response is obtained for a given amount ofnickel and manganese when the nickel to manganese ratio is about 1.0. Ifthe ratio is less than 1.0, an excess of manganese exists which can haveadverse effects on the stress corrosion resistance of the alloy. A ratiogreater than about 1.5 does not give improved results over a ratio ofabout 1.0 and is more expensive due to the high cost of the nickel.

In addition to the foregoing, the alloy of the present inventioncontains a material selected frbm the group consisting of aluminum in anamount from 0.01 to 5.0 percent, magnesium from 0.01 to 5.0 percent,boron from 0.001 to 0.1 percent and mixtures thereof. Each of theseelements act as deoxidizers and assist in the melting of the alloys.Aluminum is the preferred addition since it tends to form a protectiveoxide coating during melting. When aluminum is used as a deoxidant only,the aluminum should be added in an amount from 0.01 to 0.75 percent.Similarly, magnesium should be used in an amount from 0.01 to 0.75percent as a deoxidant. In addition, the aluminum and magnesium may beused as advantageous alloying additions in amounts greater than 0.6percent for increased corrosion resistance and fracture toughness. Thealuminum when used at the higher levels, also tends to modify thecellular precipitate at the grain boundaries.

The zinc component should be present in an amount from 0.1 to 3.5percent. Increased amounts of zinc over 3.5 percent give rise to adecrease in the stress corrosion resistance and fracture toughness.

The zinc addition controls the grain size, reduces the cellularprecipitate at the grain boundaries, changes the morphology of theinclusions, promotes sound castings and increases the aging response ofthe alloy. It is most surprising that so many advantages may be realizedfrom a single alloying addition. The grain size control may beattributed to a fine dispersoid which is present in the zinc containingalloys. The increased aging respouse is due to an increase in the growthrate of the precipitate. The preferred zinc content is from 1 to 3percent.

In addition to the foregoing, several additives are particularlyadvantageous. Tin is a particularly desirable additive in an amount from0.01 to 2 percent and preferably from 0.5 to 1.0 percent. Tin tends toalter the morphology of the cellular precipitate at the grain boundary.

Zirconium and/or titanium are preferred alloying additions in amounts0.01 to 2.0 percent each, and preferably from 0.15 to 0.30 percent each.These materials tend to desirably change morphology and chemistry ofinclusions and desirably change morphology of cellular precipitate atgrain boundaries.

In addition, chromium is a desirable addition in an amount from 0.01 to1.0 percent, and preferably from 0.15 to 0.30 percent. Chromium tends tocontrol the grain size and change the morphology and chemistry ofinclusions.

Additional desirable alloying additoins are cobalt and/or iron inamounts from 0.05 to 1.0 percent each, and preferably from 0.2 to 0.5percent each. These materials also tend to control the grain size.

Naturally, other additives may be desirable in order to achieve oraccentuate a particular property and conventional impurities may betolerated.

The casting of the alloy of the present invention is not particularlysignificant. Any convenient method of casting may be employed. Pouringtemperatures in the range of about 1,000 to 1,200C. are preferablyemployed, with an optimum pouring temperature in the range of l,050 to1,100C.

Generally, the alloy of the present invention is processed by breakdownof ingot into strip using a hot rolling operation followed by coldrolling and annealing cycles to reach final gage. Preferred propertiesare obtained using an aging treatment.

It is preferred that the starting hot rolling temperature be in therange of 700 to 900C, and preferably 780 to 900Cv The cooling rate fromhot rolling should preferably be in excess of 25C. per hour down to300C. in order to avoid precipitation of manganesenickel rich phases.The alloy is capable of cold rolling reductions in excess of 90 percent,but the cold rolling reduction should preferably be between 30 and 80percent in order to control the grain size.

It has been found that an average grain size less than 0.015 mm givesthe optimum fracture toughness. An average grain size of this order canbe obtained by control of the cold rolling reduction, annealing timesand annealing temperatures. In general, annealing temperatures in therange of 550 to 900C. for times from one minute to 10 hours can give therequired grain size.

After annealing, the material is cooled in excess of 25C. per hour downto 300C., as indicated above, and the cold rolling and annealing cyclesrepeated as desired depending on gage requirements.

The alloy of the present invention, as previously stated, may be aged inthe range of 250 to 475C, with temperatures of 380 to 460C. beingpreferred. Aging times of 30 minutes to 10 hours, with preferred timesof 1 to 6 hours, are used to obtain the desired properties. In addition,it has been found that controlling the amount of cold work prior toaging has an effect on fracture toughness and aging response. Inparticular, it has been observed that the cold work gives rise toincreased nucleation sites for the intragranular precipitation of thediscrete manganese-nickel rich particles. Hence, cold working of thealloys prior to aging at the higher temperatures of the aging rangeincreases the aging response and decreases the amount of cellularprecipitate. The amount of cold rolling can vary from 10 to 50 percent,with from 15 to 45 percent yielding the optimum fracture toughness.

The present invention will be more readily understandable from aconsideration of the following illustrative examples.

EXAMPLE I The Durville method was used to cast the various alloys listedin Table I. The copper and nickel were melted under a charcoal cover.Aluminum was added to deoxidize the melt. Following the removal of thecharcoal cover, the manganese and zinc additions were made. The slag wasremoved and the melt was poured from approximately 1080C.

TABLE 1 Composition Weight Alloy Nickel Manganese Aluminum Zinc Copper A19.72 19.92 .36 Substantially balance B 20.01 19.80 .39 2.17Substantially balance C 19.72 19.78 .39 4,25 Substantially balance D19.89 19.50 .40 6.34 Substantially balance EXAMPLE II The alloysprepared in Example I were processed in the following manner. All alloyswere homogenized at 840C. for about 2 hours. The materials were hotrolled from 1.500 inches to 0.418 inches and water quenched. The alloyswere cold rolled 60 percent to 0.16) inches. Alloys A, B and C wereannealed at 600C. for about 30 minutes and Alloy D was annealed at 625C.for about 30 minutes. After a water quench, the alloys were cold rolled60 percent to 0.067 inch and annealed and quenched again in the samemanner. Subsequent to the water quench, the alloys were cold rolled 25percent to 0.050 inches and aged at 450C. for various times. Theresultant properties were determined after various aging times. Theseare indicated in Tables 2A and 2B below. Table 2A represents theproperties longitudinal to the rolling direction and Table 2B representsthe properties transverse to the rolling direction, with a copper-2percent beryllium alloy shown for comparison. The term UPE is a relativevalue of the fracture toughness determined by the Kahn Tear Test.

The alloys were annealed at different temperatures to control the grainsize. Therefore, the effect of the various zinc additions could bedetermined independent of any effect of grain size on the alloys. Theaverage grain size of the alloys tested was 0.005 to 0.010 mm.

TABLE 2A Longitudinal Properties The data are presented in graphicalform in FIGS. 1

and 2. The fracture toughness is plotted as a function Alloy Aging Timeat Yield Strength UPE 450C, Hours 0.2% Offset in.lb./in

ksi A 2.5 170 375 A 3.0 178 220 A 3.5 184 1 19 B 2.0 187 212 B 3.5 20415 C 1.0 176 80 C 2.0 195 8 C 3.0 208 0 D 1.5 159 207 D 2.0 175 153 D2.5 182 31 Aged 316C.

Cu/ZBe 1.5 165 42 Cu/2Be 2.0 175 18 TAB LE 28 Transverse PropertiesAlloy Aging Time at Yield Strength UPE 450C, Hours 0.2% Offset1n.lb./in.

ksi

A 2.5 150 172 A 3.0 161 80 A 3.5 163 25 B 1.0 144 330 B 2.0 173 150 B3.5 204 0 C 1.0 154 42 C 2.0 183 0 C 3.0 196 0 D 1.5 157 51 D 2.0 168 15D 2.5 174 15 Aged 316C. Cu/ZBe 1.5 171 5 Cu/2Be 2.0 173 0 Cu/2Be 2.5 1780 carried out in other ways without departing from the -spirit oressential characteristics thereof. The present embodiment is thereforeto be considered as in all rejspects illustrative and not restrictive,the scope of the invention being indicated by the appended claims, andall changes which come within the meaning and range of equivalency areintended to be embraced therein.

What is claimed is:

l. A wrought copper base alloy having improved toughness and stresscorrosion resistance consisting essentially of from 12.5 to 30 percentnickel, from 12.5 to 30 percent manganese, from 0.1 to 3.5 percent zinc,and a material selected from the group consisting of aluminum from 0.01to 5 percent, magnesium from 0.01 to 5 percent, boron from 0.001 to 0.1percent and mixtures thereof, balance essentially copper, wherein thenickel to manganese ratio is from 0.75 to 1.5, said alloy having anaverage grain size less than 0.015 mm. and an intragranularprecipitation of discrete manganese-nickel rich particles.

2. An alloy according to claim 1 wherein the nickel content is from 15to 25 percent and the manganese content is from 15 to 25 percent.

3. An alloy according to claim 1 wherein said material is aluminum in anamount from 0.6 to 5 percent.

4. An alloy according to claim 1 wherein said material is magnesium inan amount from 0.6 to 5 percent.

5. An alloy according to claim 1 wherein said material is aluminum in anamount from 0.01 to 0.75 percent.

6. An alloy according to claim 1 wherein said material is magnesium inan amount from 0.01 to 0.75 percent.

7. An alloy according to claim 1 wherein the zinc content is from 1 to 3percent.

8. An alloy according to claim 1 containing a material selected from thegroup consisting of iron from 0.05 to 1 percent, cobalt from 0.05 to 1percent mixtures thereof.

2. An alloy according to claim 1 wherein the nickel content is from 15to 25 percent and the manganese content is from 15 to 25 percent.
 3. Analloy according to claim 1 wherein said material is aluminum in anamount from 0.6 to 5 percent.
 4. An alloy according to claim 1 whereinsaid material is magnesium in an amount from 0.6 to 5 percent.
 5. Analloy according to claim 1 wherein said material is aluminum in anamount from 0.01 to 0.75 percent.
 6. An alloy according to claim 1wherein said material is magnesium in an amount from 0.01 to 0.75percent.
 7. An alloy according to claim 1 wherein the zinc content isfrom 1 to 3 percent.
 8. An alloy according to claim 1 containing amaterial selected from the group consisting of iron from 0.05 to 1percent, cobalt from 0.05 to 1 percent mixtures thereof.